White light solid-state laser source

Abstract

Red light and green light are generated by passing a beam of plane-polarized blue light sequentially through two resonators each including a praseodymium-doped gain medium. A portion of the blue light is absorbed in the gain media and optically pumps the gain-media. Green light is generated in the first resonator and red light is generated in the second resonator. Green light from the first resonator is transmitted through the second resonator. Red light, green light, and unabsorbed blue light are delivered from the second resonator. Relative proportions of red light, green light, and blue light delivered from the second resonator can be varied by varying the orientation of the polarization-plane of the blue light with respect to the gain media. Sources of plane polarized blue light include optically pumped, frequency-doubled edge-emitting and surface-emitting semiconductor lasers.

1 . A method of providing a beam of light having red-light green-light and blue-light components, comprising: 
 generating a beam of blue light; and    directing said beam of blue light axially and sequentially through first and second laser resonators, each of said resonators including gain medium doped with at least praseodymium, one of said resonators being arranged to deliver green light and the other of said resonators being arranged to deliver red light in response to a first portion of said beam of blue light being absorbed by said gain-media therein, said resonators being arranged such that the beam of light having red-light, green-light, and blue-light components is delivered from said second resonator.    
     
     
         2 . The method of  claim 1 , wherein said blue light has a wavelength which is one of about 440 nm, about 444 nm, about 445 nm, about 451 nm, about 460 nm, about 467 nm, about 468 nm, and about 479 nm, wherein said green light has a wavelength of one of about 522 nm and about 545 nm, and wherein said red light has a wavelength which is one of about 639 and 644 nm.  
     
     
         3 . The method of  claim 1 , wherein each of said laser resonators is fiber laser-resonator including a length of optical fiber between fiber Bragg gratings and said praseodymium-doped gain-medium is a praseodymium-doped core of said optical fiber.  
     
     
         4 . The method of  claim 1 , wherein said gain media are crystal gain-media.  
     
     
         5 . The method of  claim 4 , wherein said praseodymium-doped crystal gain-media are selected from a group of crystal gain media consisting of Pr 3+ :YLF; Pr 3+ :Y 3 Al 5 O 12 , Pr 3+ :YAlO 3 , Pr 3+ :BaY 2 F 8 , Pr 3+ :LaF 3 , Pr 3+ :CaWO 4 , Pr 3+ :SrMoO 4 , Pr 3+ :YAG, Pr 3+ :Y 2 SiO 5 , Pr 3+ :YP 5 O 14 , Pr 3+ :LaP 5 O 14 , Pr 3+ :LuAlO 3 , Pr 3+ :LaCl 3 , and Pr 3+ :LaBr 3 .  
     
     
         6 . The method of  claim 5 , wherein said gain-media are each Pr 3+ :YLF.  
     
     
         7 . The method of  claim 5 , wherein at least one of said praseodymium doped gain-media is co-doped with one or more of erbium, holmium, dysprosium, europium, samarium, promethium, and neodymium.  
     
     
         8 . The method of  claim 4 , wherein said beam of blue light is plane-polarized, and the method further includes the step of selectively orienting the plane of polarization of said blue light with respect to said gain media for selecting specific proportions of said red-light, green light and blue light components in said beam of light delivered from said second resonator.  
     
     
         9 . The method of  claim 8 , wherein said proportions of said components are selected such that said beam of light delivered from said second resonator is a beam of white light.  
     
     
         10 . The method of  claim 1 , wherein said first resonator is arranged to deliver green light and said green light propagates axially through said second resonator together with said blue light.  
     
     
         11 . A method of providing a beam of light having red-light green-light and blue-light components, comprising: 
 generating a beam of blue light; and    directing said beam of blue light axially through first and second resonators in sequence, each of said resonators including a praseodymium-doped crystal gain-medium, said first resonator being arranged to deliver green light in response to a first portion of said blue light being absorbed by said gain-medium therein and said second resonator being arranged to deliver red light in response to a portion of said first residual portion of said blue light being absorbed by said second gain-medium while transmitting said green light and a second residual portion of said blue light, whereby the beam of light having red-light, green-light, and blue-light components is delivered by said second resonator.    
     
     
         12 . The method of  claim 11 , wherein each of said gain-media is Pr 3+ :YLF.  
     
     
         13 . The method of  claim 11 , wherein said each of said laser resonators is formed between mirrors deposited on said crystal gain-medium.  
     
     
         14 . Laser apparatus comprising: 
 a light source arranged to deliver a beam of blue light;    first and second laser resonators each thereof formed between first and second reflectors and having a praseodymium-doped gain-medium disposed between said first and second reflectors;    said laser and said first and second laser-resonators arranged such that said beam of blue light passes sequentially through said first and second laser-resonators with a portion of said blue light being absorbed by each of said gain media and an unabsorbed portion of said blue light being transmitted by said second laser resonator; and    wherein one of said first and second laser resonators is arranged to generate green light in response to said absorption of blue light and the other of said first and second laser resonators is arranged to generate red light in response to said absorption of blue light, and said green and red light is transmitted from said second resonator together with said unabsorbed portion of said blue light.    
     
     
         15 . The apparatus of  claim 14 , wherein said first laser-resonator is arranged to generate green-light.  
     
     
         16 . The apparatus of  claim 14 , wherein said gain media are crystal gain media each thereof having first and second opposite ends and said first and second mirrors of said laser resonators are deposited on first and second opposite ends of said gain-media.  
     
     
         17 . The apparatus of  claim 14 , wherein said gain media are crystal gain media each thereof having first and second opposite ends and said first and second mirrors of said laser resonators are axially spaced apart from said ends of said gain media.  
     
     
         18 . The apparatus of  claim 14 , wherein each of said first and second laser-resonators includes an optical fiber, wherein a length of the core of said optical fiber provides said gain medium, and wherein said second reflectors of each resonator are fiber Bragg gratings written into the core of said optical fiber at opposite ends of the gain-medium-providing length thereof.  
     
     
         19 . The apparatus of  claim 14 , wherein said light source includes one of a frequency-doubled surface-emitting semiconductor laser, a frequency-doubled surface-emitting semiconductor laser, a surface-emitting semiconductor laser delivering fundamental radiation, an edge-emitting semiconductor laser delivering fundamental radiation, and a light-emitting diode.  
     
     
         20 . Laser apparatus comprising: 
 a laser arranged to deliver a beam of plane-polarized blue light;    first and second laser resonators each thereof formed between first and second reflectors and having a praseodymium-doped crystal gain-medium disposed between said first and second reflectors, said crystal gain-medium having a crystal axis;    said laser and said first and second laser-resonators arranged such that said beam of blue light propagated along an optical path sequentially through said first and second laser-resonators, with a first portion of said blue-light beam being absorbed in said gain medium of said first laser-resonator, a second portion of said blue-light beam being absorbed in said gain medium of said second laser-resonator, and an unabsorbed third portion of said blue-light beam being delivered from said second resonator;    said first laser resonator being further arranged to deliver green light in response to said absorption of said first portion of said blue-light beam by said gain medium thereof; and    said second laser resonator being further arranged to deliver red light in response to said absorption of said first portion of said blue-light beam by said gain medium thereof, and to receive, transmit and deliver green-light delivered from said first laser resonator, such that red-light green-light and blue-light are delivered from said second laser-resonator.    
     
     
         21 . The apparatus of  claim 20 , wherein said further including means for selectively adjusting the orientation of the polarization-plane of said blue-light with respect to the crystal axis of at least one of said gain-media.  
     
     
         22 . The apparatus of  claim 21 , wherein said polarization-plane-orientation adjusting means includes a polarization rotator located in the path of the blue-light beam between said laser and said at least one of the gain-media, said polarizer being and selectively rotatable about the path of said blue-light beam.  
     
     
         23 . The apparatus of  claim 20 , wherein at least one of said gain media is selectively rotatable about the path of said blue light beam for selectively adjusting the orientation of the polarization-plane of said blue-light with respect to the crystal axis of said at least one of the gain media.  
     
     
         24 . Laser apparatus comprising: 
 a laser arranged to deliver a first beam of blue-light;    an optical arrangement for dividing said first blue-light beam into second third and fourth blue-light beams;    first and second fiber laser-resonators each thereof including an optical fiber having a praseodymium-doped core;    a first optical arrangement for coupling said second blue-light beam into said first fiber laser-resonator and a second optical arrangement for coupling said third blue-light beam into said second laser resonator;    said first fiber laser-resonator arranged to deliver green light in response to absorption of at least a portion of said second blue-light beam by said praseodymium-doped core of said first fiber laser-resonator; said second fiber laser-resonator arranged to deliver green light in response to absorption of at least a portion of third second blue-light beam by said praseodymium-doped core of said second fiber laser-resonator; and    wherein said green light delivered by said first fiber laser-resonator, said green light delivered by said second fiber laser-resonator, and blue-light from said fourth blue light beam are fiber-coupled into a common output fiber of the appartus.    
     
     
         25 . The apparatus of  claim 24 , further including means for selectively varying proportions of said first blue-light beam in said second third and fourth blue light beams, thereby varying the proportions of red light, green light, and blue light coupled into said common output fiber.  
     
     
         26 . The apparatus of  claim 24 , wherein said first blue-light beam is plane polarized and said selective variation means includes a first polarizing beamsplitter located in said first blue-light beam and a polarization rotator located in said first blue-light beam between said polarizing beamsplitter and the laser.  
     
     
         27 . The apparatus of  claim 26 , wherein said selective-variation means includes a second polarizing beamsplitter located in second first blue-light beam and a second polarization rotator located in said second blue-light beam between said second polarizing beamsplitter and said first polarizing beamsplitter.  
     
     
         28 . Laser apparatus; comprising: 
 a frequency-doubled edge-emitting semiconductor laser; and    a laser resonator including a gain-medium doped with at least praseodymium, said gain medium arranged to be energized by blue light delivered by said frequency-doubled edge-emitting semiconductor laser.    
     
     
         29 . The apparatus of  claim 28 , wherein said gain-medium is a crystal gain-medium.  
     
     
         30 . The apparatus of  claim 29 , wherein the material of said crystal gain-medium is selected from the group of materials consisting of YLF; Y 3 Al 5 O 12 , YAlO 3 , BaY 2 F 8 , LaF 3 , CaWO 4 , SrMoO 4 , YAG, Y 2  SiO 5 , YP 5 O 14 , LaP 5 O 14 , LuAlO 3 , LaCl 3 , and LaBr 3 .  
     
     
         31 . The apparatus of  claim 29 , wherein said gain-medium is co-doped with one or more of erbium, holmium, dysprosium, europium, samarium, promethium, and neodymium.  
     
     
         32 . The apparatus of  claim 28 , wherein said laser-resonator is a fiber laser-resonator.  
     
     
         33 . The apparatus of  claim 28 , wherein said blue light has a wavelength of about 479 nm.  
     
     
         34 . A laser apparatus comprising: 
 a first laser resonator having a praseodymium doped gain medium and including wavelength selective optics configured such that the resonator will generate green light when the gain medium is optically pumped:    a second laser resonator having a praseodymium doped gain medium and including wavelength selective optics configured such that the resonator will generate red light when the gain medium is optically pumped; and    a source of blue light for optically pumping the first and second laser resonators, said resonators being arranged such that the blue light first enters the first resonator and wherein at least some of the blue light not absorbed therein then passes into the second resonator along with the green light generated by the first resonator and wherein the output of the second resonator includes blue, green and red light.